Threaded nut members made by stamping from generally flat, sheet metal stock are well known and examples of such nut members can be seen from the U.S. Pat. No. 2,378,957 issued Jun. 26, 1945 to G. A. Tinnerman for Fastening Device and U.S. Pat. No. 2,090,640 issued Aug. 24, 1937 to H. Rosenberg for Capped Nut and Art for Producing Same.
In the present invention a lightweight threaded nut member which can be formed from flat sheet metal stock is provided having a high strength to weight ratio. For example with the construction of the present invention a lightweight flanged nut can be formed which has around 80% of the strength of a conventional solid flanged nut of comparable size while having only around one third of its weight.
In the present invention a unique scalloped configuration is utilized which provides the nut member with an outer contour facilitating gripping by a conventional multisided wrench and an inner contour which facilitates the formation of a thread having a high percentage thread engagement with the mating threaded bolt or other threaded member and hence provides a high strength thread. Thus the nut member of the present invention is formed from flat sheet metal into a structure having an essentially uniform cylindrical barrel having an enlarged flange at one end. The nut can also be constructed without a flange. Next the barrel is deformed radially inwardly at a plurality of locations to form radially inwardly, extending lobes having arcuate surfaces spaced from radially outwardly extending lobe having arcuate surfaces. Next an internal or female thread is formed on the inner lobes. While the thread form can be made by metal removal in cutting, it is preferably made by form taps; that is taps that displace metal instead of cutting metal away. As will be seen the result is a lightweight fastener having a high strength to weight ratio and which is of a relatively inexpensive construction.
The unique nut construction also facilitates the provision of a prevailing torque feature. In addition a continuous ring or collar can be added at the top of the barrel of the nut with continuous threads to provide sealing at that end and some increase in thread strength. The nut construction and method of the present invention also facilitates the nut structure being formed integrally with a larger sheet metal part such as a bracket or body member.
Thus it is an object of the present invention to provide a unique, lightweight nut member formed from sheet metal and having a scalloped construction defined by circumferentially alternating radially inner and outer extending lobes.
It is another object of the present invention to provide a unique sheet metal nut and method of construction.
Other objects, features, and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings: